A day after two explosions killed three people and injured more than 150 at the Boston Marathon, details emerged about the investigation and the victims.

One of the victims was 8-year-old Martin Richard of Dorchester, who was waiting with his mother and sisters for his father to cross the finish line.

His mother and one of the girls suffered what were described as "grevious" injuries, according to the Boston Globe. Another child was not hurt.[embedgallery id=134983]

[videoembed id=134930]"They are beloved by this community," Boston City Councilor Ayanna Pressley said of the Richard family, at a gathering in Dorchester. "They contribute in many ways. That’s why you see this outpouring. It’s surreal, it’s tragic, it’s incomprehensible. Everyone here tonight is trying to comfort one another and be prayerful."

More than 150 people were treated at Boston area hospitals, with injuries ranging from lost limbs to lacerations. Several patients suffered shrapnel-type wounds.

"This is something I've never seen in my 25 years here — this amount of carnage in the civilian population," Dr. Alisdair Conn, chief of emergency services at Massachusetts General Hospital, said Monday afternoon. "This is what we expect from war."

State police confirmed that an apartment in Revere was searched overnight, but would not provide details. The Revere Fire Department said on its Facebook page that it was on scene to assist authorities looking for a "person of interest."

Television footage showed officers removing bags from the Ocean Avenue apartment. CBS Boston reported that federal agents questioned two men at the building who were later released.

The FBI is leading the investigation, and said no arrests had been made.

"It is a criminal investigation that is a potential terrorist investigation," Richard DesLauriers, the FBI special agent in charge for Boston, said Monday.

Investigators urged people with information about the explosions — especially those with photos or video — to contact them at 800-494-TIPS or 800-CALL-FBI.

"No piece of information or detail is too small," the FBI said in a statement.

The City of Boston planned to reopen a resource and information centerat the Park Plaza Castle on Arlington Street at 9 a.m. Tuesday. Counseling and shelter services were being offered, and runners would be able to claim belongings left on the marathon route.

More streets around the blast site were back open Tuesday morning, although Boylston Street remained closed between Massachusetts Avenue and Berkeley Street. The city's website included an updated map of the crime scene.

Several businesses in the immediate area also planned to stay closed Tuesday. Boston Police tweeted that the Prudential Center was accessible from Huntington Avenue, and that cars would be allowed on Newbury Street.

On its website, the MBTA said subways lines were running normally, but that the Green Line Copley station would not open. Several bus lines were either rerouted or cancelled.

Transit police told passengers to expect an increased law enforcement presence on public transit, including bag searches, and urged people to contact them about anything suspicious.

UMass Boston, Emerson College and Berklee School of Music were all closed Tuesday.

With additional reporting from Reuters.Follow Metro Boston on Twitter: @MetroBos